Balanced-free piston engine

ABSTRACT

Unsymmetrical, synchronized, balanced, free piston engines are disclosed in which a synchronizer-balancer assembly provides balanced operation of the engine by connection to both the engine and a movable member of an energy-absorbing device to be driven by the engine, in order to transmit the reciprocatory power output from the engine to the energy-absorbing device through the synchronizer-balancer assembly. Power within the engine is provided in one embodiment by an alternately acting double-acting power section including a double-acting power piston. The power piston is connected to move with a first portion of the synchronizer-balancer assembly to cause the oppositely directed translational movement, with respect to the engine housing, of a counterbalancing second portion of the synchronizer-balancer, and a movable driving member or other movable member of the energyabsorbing device is connected to move with the counterbalancing second portion in alternating opposite directions from the power piston and first portion. Engines incorporating energy-absorbing devices in the form of a pump, an electrical generator, and a double-acting reciprocal compressor are shown. Also shown are alternate embodiments in which the alternately acting doubleacting power section and its double-acting power piston are replaced by a pair of alternately acting single-acting power sections with a pair of single-acting power pistons, one in each such section.

United States Patent [72] Inventor Anton Braun 6421 Warren Ave., Minneapolis, Minn. 55435 {21] Appl. No. 876,704 [22] Filed Nov. 14,1969 [45] Patented Oct. 5, 1971 [54] BALANCED-FREE PISTON ENGINE 21 Claims, 12 Drawing Figs.

[52] U.S.Cl 123/46 R, 123/192 B, 290/1 R,417/364 [51] Int.Cl ..F02b 71/04, H02k 35/00, F04b 35/00 [50] Field oiSearch l23/46,46 B, 46 SA, 46 A, 46 H, 46 E, 46 SC, 192, 192 B; 417/364; 290/1 R, I A

[56] References Cited UNITED STATES PATENTS 662,631 11/1900 Steele 123/192 1,741,731 12/1929 Nordensson.. 123/46 A 2,407,790 9/1946 Tourneau..... 123/46 A 2,991,773 7/1961 Cadiou 123/46 SC FOREIGN PATENTS 640,650 5/1962 Canada 123/46 A 1,108,002 5/1961 Germany 123/46 E i 52 12 41b 29 27 E 21 Primary Examiner-Wendell E. Burns Attorneys-Frederick E. Lange, William C. Babcock, John J.

Held, Jr. and Bruce A. Nemer ABSTRACT: Unsymmetrical, synchronized, balanced, free piston engines are disclosed in which a synchronizer-balancer assembly provides balanced operation of the engine by connection to both the engine and a movable member of an energy-absorbing device to be driven by the engine, in order to transmit the reciprocatory power output from the engine to the energy-absorbing device through the synchronizerbalancer assembly. Power within the engine is provided in one embodiment by an alternately acting double-acting power section including a double-acting power piston. The power piston is connected to move with a first portion of the synchronizerbalancer assembly to cause the oppositely directed translational movement, with respect to the engine housing, of a counterbalancing second portion of the synchronizerbalancer, and a movable driving member or other movable member of the energy-absorbing device is connected to move with the counterbalancing second portion in alternating 0pposite directions from the power piston and first portion. Engines incorporating energy-absorbing devices in the form of a pump, an electrical generator, and a double-acting reciprocal compressor are shown. Also shown are alternate embodiments in which the alternately acting double-acting power section and its double-acting powerpiston are replaced by a pair of alternately acting single-acting power sections with a pair of single-acting power pistons, one in each such section.

BALANCED-FREE PISTON ENGINE BACKGROUND This invention relates to free piston engines, particularly to unsymmetrical, synchronized, balanced, free piston engines, and more particularly to unsymmetrical, synchronized, balanced, free piston engines in which at least two alternately acting power pistons provide power for transmission to a reciprocally movable member or members of an energy-absorbing device.

Prior free piston engines exist which are unsymmetrical, synchronized, and balanced and which use a power section to provide power to a reciprocally movable member of an energy-absorbing device and a bouncer section to return the power piston to a point in the power cylinder where repetitive combustion can occur. However, an engine using a bouncer compressor as the primary means to return the power piston toward successive firing positions does not have a naturally equal stroke-time function on both strokes of the movable member of the energy-absorbing device, and the work output is limited by the availability of a combustion power stroke in only one direction.

There are also prior symmetrical, synchronized, balanced, free piston engines which have had alternately acting power pistons, and which were balanced by the counter movement of a working cylinder, such as a power cylinder or a compressor cylinder. The movement of these working cylinders complicated the engine and presented a control problem in providing the fuel to the moving cylinder and allowing exhaust gases and compressed air output to escape from the moving cylinder. Also, these engines were not readily adaptable to perform as a power package and provide power to various types of energy absorbing devices which accept a reciprocatory power input.

There are other symmetrical prior free piston engines using alternately acting power pistons which have used countermoving piston assemblies to balance the engine. These engines were also not readily adaptable for use with energy-absorbing devices other than the particular device they were specifically designed to operate.

SUMMARY Free piston engines according to the present invention are unsymmetrical, synchronized, balanced, free piston engines adapted to drive various energy absorbing devices which accept a reciprocatory power input. The engine includes two alternately acting power pistons which may be rigidly interconnected as parts of a double-acting piston member in one double-acting power section or cylinder, or which preferably are separate interconnected single-acting piston members, one of which is positioned in each of two-spaced single-acting power sections or cylinders. The two-power pistons are connected to drive and move with a first reciprocally movable portion of a synchronizer-balancer assembly, which also has a movable counterbalancing portion moving reciprocally and oppositely to the first portion. The two-power pistons and the first movable portion of the synchronizer-balancer assembly form a power assembly, reciprocal movement of which causes mechanically synchronized reciprocal movement of the movable counterbalancing portion in a direction opposite to the direction of movement of the power assembly. A movable driving member or other movable member associated with or forming a part of the energy-absorbing device to be driven by the engine is connected with the movable counterbalancing portion-of the synchronizer'balancer assembly for reciprocal movement with it. The invention preferably also includes means for adjusting the effective weight associated with and moving with the movable counterbalancing portion of the synchronizer-balancer assembly.

Free piston engines of the present invention are simple and compact engines which provide twice the work output per cycle with the same capacity synchronizer and with significantly less than a factor of two increase in the overall size and 5 pressure rise occurs alternately in each combustion chamber as each respective power piston approaches its top-deadcenter position. This high rate of pressure rise in the combustion chamber renders the engine relatively "stiff at both ends of its stroke; that is, the power pistons traveling in one direction are caused to stop and return" or to travel in the opposite direction by a force which increases at a very high rate as the power pistons approach their top-dead-center positions, all without a bouncer compressor. This stiff characteristic of the engine is particularly useful when the energy absorbing device is a double-acting reciprocal compressor because the stiff" characteristic prevents any significant compressor piston travel beyond the desired nominal point, i.e., it permits a low overstroke requirement to be adopted in the compressor which, in turn, results in the compressor being able to have a small clearance volume per given output, or a high volumetric efficiency. Therefore, a smaller compressor piston may be used, and the overall size of the engine may be correspondingly reduced.

Free piston engines of the present invention also allow a higher speed, hence a higher power output, other factors being equal. A higher speed may be obtained because a movable member of the energy-absorbing device is attached to and moves with the counterbalancing portion of the synchronizerbalancer assembly and not with the power assembly. Thus, in a counterbalancing portion of the synchronizer-balancer assembly. Since the counterbalancing portion of the synchronizer-balancer assembly compensates for the weight of the power assembly, the weight of the counterbalancing part in this invention may be reduced by twice the weight of the movable member of the energy-absorbing device, i.e., not

only is the power assembly lighter by the weight of the movable member but the weight of the movable member must be considered as part of the weight of the counterbalancing portion. Thus, the entire weight of the moving assemblies is reduced. Since one of the factors in determining the maximum piston speed of a free piston engine is the weight associated with the moving assemblies which must continually start and stop and reverse direction, removing weight from the power assembly and from the parts associated to move with the counterbalancing portion of the syychronizer-balancer assembly increases the maximum possible piston speed attainable.

Free piston engines according to the present invention can provide a naturally equal stroke-time function on both strokes of the movable member of the energy-absorbing device driven by the engine. Where a hydrostatic pump is the energy-absorbing device driven by the engine, larger dampers or accumulators would be needed to smooth the flow without this naturally equal stroke-time function provided by engines of the present invention. Engines of the present invention allow a smaller damper size for any given pump, as compared to engines without an equal stroke-time function. Where an AC generator is the energy absorbing device driven by the engine, an unacceptably high DC component could be provided from the AC generator because of the asymmetry of the output is, because of the flexible nature of the present invention, it is readily adaptable to perform as a power package and to provide power to various types of energy-absorbing devices which accept a reciprocatory power input.

It is thus an object of the present invention to provide improved, unsymmetrical, synchronized, balanced, free piston engines which are sufficiently simple, compact and flexible in their nature to accept various kinds of energy-absorbing devices and to be capable of driving them at relatively high speed and with relatively high specific output (e.g. horsepower per pound of engine weight).

It is another object of the present invention to provide novel, unsymmetrical, synchronized, balanced free piston engines in which substantially all of the reciprocatory power output of two alternately acting interconnected power pistons is transmitted to an energy-absorbing device through a synchronizer-balancer assembly in which a first portion of the assembly is connected to the pistons and a counterbalancing portion of the assembly is connected to a movable member of the energy-absorbing device.

It is a further object of the present invention to provide novel, unsymmetrical, synchronized, balanced free piston engines which use interconnected alternately acting power pistons to provide reciprocatory power for transmission to an energy-absorbing device and in which a movable member associated with the energy-absorbing device is connected to move with and constitute part of the effective weight of a counterbalancing portion of a synchronizing and balancing mechanism within the engine.

These and further objects and advantages of the present invention will become clear in the light of the following detailed description of the illustrative embodiments of this invention as shown in the drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical cross-sectional view of an embodiment of the improved, free piston engine of the present invention shown connected with an energy-absorbing device.

FIG. 2 is a vertical cross-sectional view taken along the section line 22 in FIG. 1.

FIG. 3 is a partial, horizontal, cross-sectional view taken along the section line 3-3 in FIG. 2, with certain parts broken away and others omitted for clarity.

FIG. 4A is a schematic, vertical, cross-sectional view of another embodiment of the improved free piston engine of the present invention shown as connected with a fluid pump.

FIG. 4B is a schematic, vertical, cross-sectional view taken along the section line 4B-4B in FIG. 4A.

FIG. 5 is a schematic, vertical, cross-sectional view of still another embodiment of the improved, free piston engine of the present invention shown connected with an electrical generator.

FIG. 6 is a schematic, vertical, cross-sectional view of still another embodiment of the improved, free piston engine of the present invention shown connected with a double-acting reciprocal compressor.

FIGS. 7 and 8 are pressure-volume curves illustrating one advantage of engines according to the present invention.

FIG. 9 is a graphical representation of velocity plotted versus stroke to illustrate another advantage of engines according to the present invention.

FIGS. 10 and 11 show vertical cross-sectional views of the end portions of other embodiments of the invention in which two alternately acting, single-acting power sections, each with a single-acting power piston therein, are located at opposite ends 'of modified engines according to the present invention, in lieu of the double-acting power section and its double-acting power piston shown in the engines of FIGS. 1, 4A, 5 and 6.

Where used in the various figures of the drawings, the same reference numerals designate the same or similar parts or elemoms in the various embodiments of the engine shown. Furthermore, when the terms right," left," right end, and left end"- are used herein, it should be understood that these terms have reference only to the structure shown in the drawings as it would appear to a person viewing the drawings, and are utilized only to facilitate describing the invention.

DESCRIPTION FIG. 1 Embodiment An improved, balanced, free piston engine 11 of the present invention is generally shown in FIGS. I and 2. The free piston engine 11 includes a power section 12 and a synchronizerbalancer section 13. An energy-absorbing device, shown diagrammatically at 14, is spaced from the right end of the synchronizer-balancer section 13. The energy-absorbing device 14 may be a liquid pump, an electrical generator, a double-acting reciprocal compressor, or any other device which utilizes or absorbs reciprocatory power. Any such device may have a variety of different specific forms and details of construction.

The power section 12 includes a cylindrical housing 15 which has a power cylinder 16 formed therein. A double-acting power piston 17 is positioned within the cylinder 16 for reciprocal movement therein substantially parallel to the longitudinal axis of the cylinder 16. The piston includes a first or outer power piston portion or face 18, a second or inner power piston portion or face 19 and a generally annular portion 21 interconnecting the outer power piston portion 18 and the inner power piston portion 19 such that they reciprocate together as a unit and form a single, alternately acting, doubleacting power piston member. Piston rings 22 are carried in grooves formed in the piston 17 for minimizing the leakage of gases between cylinder 16 and the piston member 17.

The left end 23 of the housing 15 is closed by a cylinder head 24 which is bolted to the end 23 of the housing 15 by a plurality of bolts, one of which is shown at 25. The cylinder head 24 together with the outer power face 18 of the piston 17 define a first or outer combustion chamber 26 in the cylinder 16. A conventional fuel injector unit 27 is positioned in an aperture 28 formed in the cylinder head 24 so that its inner end communicates with chamber 26.

Similarly, the right end 29 of the housing 15 is closed by a cylinder head 34 which is bolted to the end 29 of the housing 15 by a plurality of bolts, one of which is shown at 30. The cylinder head 34 together with the inner face 19 of the piston 17 define a second or inner combustion chamber 31 in the cylinder 16. A further conventional fuel injector unit 32 is positioned in an aperture 33 formed in the cylinder head 34 so that the inner end of fuel injector 32 communicates with the inner combustion chamber 31.

The inner cylinder head 34 also forms a wall between the power section 12 and a synchronizer-balancer section 13, and, in order to provide a connection between the power section and the synchronizer-balancer section, the cylinder head 34 has a central aperture 36 formed therein so that the central longitudinal axes of the aperture 36 and the cylinder 16 are coaxial. Conventional combustion chamber shaft seals 37 are positioned in the aperture 36, for reasons hereinafter explained. Shaft seals 37 must withstand the temperature and pressure of the combustion chamber 31, but seals of this kind are well known in the art.

A duct 39 is shown connected with housing 15 to provide communication between a plurality of peripherally spaced dual inlet ports or openings, one set or pair of which dual ports is shown formed in the housing 15 at 41a and 41b, and a source of air or fuel-air mixture, not shown. A plurality of peripherally spaced dual exhaust ports or openings, one set of which dual ports is shown formed in housing 15 at 42a and 42b, permit combustion gas in the combustion chambers 26 and 31 to be exhausted from cylinder 16. To insure proper blowdown" the outermost edges of the ports 41a and 41b are positioned such that the projection of these outermost edges on the central longitudinal axis of cylinder 16 is within the projection of the outermost edges of the ports 42a and 42b on the central longitudinal axis of cylinder 16. The ports 41 and 42 are further arranged, relative to the combustion chambers 26 and 31, so that the chambers will be properly scavenged during normal operation of the engine. That is, as the power piston 17 approaches its rightmost position, exhaust ports 42a are opened, and exhaust gases can blow down to the approximate pressure of the fresh charge of air or fuel-air mixture that exists in duct 39 at the time inlet ports 410 are opened. As the inlet ports 41a are opened by piston 17, the air or fuel-air mixture from the source, not shown, can enter chamber 26 through duct 39 and ports 41a, and this fresh charge of air or fuel-air mixture can scavenge chamber 26 to provide a fresh charge for the next alternating power stroke in chamber 26. With the piston 17 traveling towards its leftmost position, exhaust gases within combustion chamber 31 can similarly "blow down through exhaust ports 42b, and chamber 31 can be similarly scavenged through duct 39, inlet ports 41b, and exhaust ports 42b.

Piston 17 is fastened to the left end of a shaft 44 by means of a bolt 45. The right end of shaft 44 is connected with the left end of a double-rack member 46 by another bolt 47. Rack member 46 constitutes a first movable portion of a synchronizer-balancer assembly 62 included in the combination of the present invention. The shaft 44 interconnecting the power piston 17 and the double-rack member 46 extends into the synchronizer-balancer section 13 of the engine through the aperture 36 formed in the cylinder head 34 and is sealed by the conventional combustion chamber shaft seals 37 positioned in this aperture 36 so as to minimize the leakage of gas and lubricant between the shaft and the aperture.

The power piston portions 18 and 19 of piston member 17 are interconnected with the first movable portion 46 of the synchronizer-balancer assembly as parts of a power assembly 43 which is supported for translational reciprocating movement as a unit back and forth along the central longitudinal axis of the power cylinder sections and piston portions. Thus, in engine 11, the power assembly 43 includes the double-acting power piston member 17, the shaft 44, the double rack member 46, together with the bolts 45 and 47 and any other fastening means utilized to interconnect the aforementioned parts, and the piston rings 22.

The synchronizer-balancer section 13 includes housing portion 49, which, as noted above, has its left end closed by cylinder head 34. Bolts 35, two of which are shown in FIG. 1, are used to fasten the housing 49 to cylinder head 34. An end wall 51 closes the right end of the housing 49 and is formed integrally with a sidewall 52 of the housing 49, as shown in FIG. 1. Of course, if desired, the end wall 51 could also be a separate member attached to the housing 49 by a plurality of bolts.

The engine combination of the present invention includes a synchronizer-balancer assembly 62 mounted within the housing 49. As noted above, the synchronizer-balancer assembly 62 includes a first movable portion which in this embodiment is shown as a double rack member 46. This rack is connected as part of the power assembly 43, for translational reciprocating movement of the power assembly parts as a unit. The balancing and synchronizing assembly 62 also includes a second movable counterbalancing portion to be described below, and means interconnecting these first and second movable portions. The interconnecting means has a pair of pinions 63 and 64 which are mounted for rotation about fixed axes on a pair of shafts 65 and 66, respectively. The ends of the shafts 65 and 66 are supported by a pair of fixed side plates 67 and 68, which are positioned on opposite sides of the double-rack member 46. One end of each of the plates 67 and 68 is secured to the right face of the cylinder head 34, and each plate extends towards the end wall 51 of the housing 49. The plates 67 and 68 are spaced equal distances on each side of the double-rack member 46, so that the member 46 can slide freely between the plates 67 and 68. The plates are substantially parallel to each other and to the central longitudinal axis of the power cylinder sections, which is also the axis of translational movement of power assembly 43.

The shafts 65 and 66 are supported by the plates 67 and 68 approximately midway between the cylinder head 34 and the end wall 51 and are positioned vertically above and below, i.e., on opposite sides of, the longitudinal central axis of the double-rack member 46. They are equidistant from the member 46, with the central longitudinal axes of the shafts 65 and 66 being arranged at 90 to the central longitudinal axes' of the power assembly 43. The distance between the plates 67 and 68 is sufficient so that the pinions 63 and 64 can rotate freely between the plates.

The double-rack member 46 includes upper and lower racks 71 and 72 which are formed in the back-to-back fashion so that the teeth thereof project in opposite directions outwardly from the member 46. The teeth of the racks 71 and 72 are arranged so that there is always engagement between the teeth of the racks 71 and 72 and the teeth of the pinions 63 and 64, respectively, whereby reciprocatory movement of the power assembly, and the racks 71 and 72, causes corresponding rotatory movement of the pinions 63 and 64.

The movable second or counterbalancing portion of synchronizer-balancer assembly 62 includes a pair of movable side plates or wall members 73 and 74 which are positioned adjacent and parallel to the fixed side support plates 67 and 68, respectively. The movable members 73 and 74 are positioned a greater distance from the double-rack member 46 than the plates 67 and 68 so that the movable members 73 and 74 can slide freely outside the fixed plates 67 and 68. A pair of racks 75 and 76 are carried by and positioned between the upper and lower ends of the movable wall members 73 and 74, as shown in FIG. 2. A plurality of pins or rivets, two of which are shown at 77, extend through the racks 75 and 76 and the upper and lower edges of the movable members 73 and 74 and are used to secure the racks 75 and 76 to the movable members 73 and 74. The racks 75 and 76 are positioned so that the teeth thereof project inwardly toward the teeth of the racks 71 and 72, respectively, and engage the pinions 63 and 64, respectively, diametrically oppositely the points of engagement between the teeth of the pinions 63 and 64 and the racks 71 and 72, respectively.

Thus, as best shown in FIG. 2, the second or movable counterbalancing portion of the synchronizer-balancer assembly 62, including side plates 73 and 74 and racks 75 and 76, can reciprocate freely in translational movement along the same central longitudinal axis of translational movement of the power assembly which includes rack portions 46, 71 and 72 and the power pistons. The interconnecting means including pinions 63 and 74 insure translational movement of the counterbalancing portion in the opposite directions and in direct response to the axial translational movements of the first movable portion, 46, 71, 72 of the synchronizer-balancer assembly. As also shown in FIG. 2, each of the movable portions of this assembly has its parts arranged so that the mass of each portion is symmetrically distributed or balanced with reference to the common central longitudinal axis of relative translational movement.

Moreover, because the racks 75 and 76 are secured together by the movable members 73 and 74 so as to prevent relative movement therebetween and because the racks 71 and 72 are integrally formed in a back-to-back relationship on the double rack member 46, the normal components of the forces created by the transmission of forces between the teeth of the racks and pinions are balanced. This arrangement of the racks and pinions eliminates a major cause of frictional losses and minimizes the energy losses, due to friction, resulting from the transfer of forces between the movable counterbalancing portion of the synchronizer-balancer assembly 62 and the power assembly 43. Furthermore, frictional losses and dynamic loading of the gear teeth, due to manufacturing errors, are further reduced by the fact that the racks 71 and 72 tend to float between, and the racks 75 and 76 tend to float" on the pinions 63 and 64 and are self-aligning in that they inherently seek a position, relative to the pinions 63 and 64, in which the dynamic forces created by the engagement between the teeth of the racks 71, 72, 75 and 76, and the pinions 63 and 64 are minimized.

The energy absorbing device is structurally interconnected with the synchronizer-balancer assembly 62, in a manner hereinafter explained, and the energy generated by the power assembly 43 is transferred, according to the present invention through the synchronizenbalancer assembly 62 to the movable driving member 14 of the desired energy-absorbing device.

The connection between the synchronizer-balancer assembly 62 and the energy-absorbing device may best be seen with reference to FIGS. 2 and 3 where bosses 91 and 92 are shown as integrally formed upon movable wall members 73 and 74 respectively, of the movable counterbalancing portion of the assembly. A pair of shafts 93 and 94 extend between the bosses 91 and 92, respectively, and the energy-absorbing device to interconnect the counterbalancing portion of the synchronizer-balancer assembly 62 with the movable member 14 of the energy-absorbing device.

More particularly, the shafts 93 and 94 shown in FIG. 3 have threads formed upon one end and the threaded ends of shafts 93 and 94 are secured within tapped holes formed in bosses 91 and 92. The other ends of shafts 93 and 94 extend through apertures 94 within wall 51 and connect to movable member 14 of the energy-absorbing device. Conventional shaft seals 96 are positioned in the apertures 97 within wall 51 to minimize the leakage of gas and lubricant between the shafts 93 and 94 and the apertures 97 during the reciprocation of the shafts 93 and 94. The shafts 93 and 94 are both parallel to shaft 44. Thus, movable member 14 of the energy-absorbing device is connected for reciprocating translational movement with the movable counterbalancing portion of the synchronizer-balancer and is, in effect, driven by the counterbalancing portion.

To achieve dynamic balance, the absolute value of the product of the sum of all the weights associated to move with the movable counterbalancing portion of the synchronizerbalancer assembly 62 times the corresponding distances all these weights move during a stroke of the engine must be equal to the product of the sum of all the weights associated to move with the power assembly 43 times the length of the corresponding stroke of the assembly 43 in the opposite direction. As noted above, the counterbalancing movable portion of the synchronizer-balancer assembly 62 includes the weights of the movable members 73 and 74, the pins 77, and the weight of the racks 75 and 76, as well as any supplemental weight members 210 and 212 which are described below. Thus the number and size of these parts, as specifically shown and described, provide a greater weight for this counterbalancing portion of the synchronizer-balancer assembly than the weight required to balance only the first movable portion of that assembly, i.e. the double-rack member 46, with its inner racks 71, 72.

The engine 11 is suitable for use with various different energy-absorbing devices, and thus the weight of the movable element 14 of the energy-absorbing device, which is attached to and carried by the right end of the shafts 93 and 94, may vary depending on the type of energy-absorbing device being driven by the engine, and particularly depending on the nature and'mass of the movable member itself. To facilitate the use of the engine in such different combinations, the movable counterbalancing portion of the synchronizer-balancer assembly has been provided with means for adjustment of its effective weight. For this purpose, the movable members 73 and 74 have been designed so that they can be readily removed and replaced by movable wall members of different weights, so that the counterbalancing movable weight of the balancing and synchronizing assembly 62 may be easily varied without affecting structure or operation of the engine. Alternately, weight may easily be removed from or added to movable wall members 73 and 74 without replacing them, for example by the use of separate supplemental weight members 210 and 212 (FIG. 2) secured by bolts 214 to wall members 73 and 74. In this way, standard movable members 73 and 74 may serve for a number of different energy-absorbing devices.

Engines according to this invention can be manufactured and sold as essentially standard units, fully balanced and useful for driving a variety of energy-absorbing devices. To the extent that the movable driving member or other movable members of the load device contribute additional effective weight moving one way or the other in translation 6 along the path of movement of the power assembly and of the counterbalancing portion' of the synchronizer-balancer assembly, the weight of the counterbalancing portion may be readily and conveniently adjusted to maintain the desired total effective balance. Thus one of the movable portions of the synchronizer-balancer assembly will have greater weight than the other, for proper balance as just described.

OPERATIONS Briefly, the operation of engine 11 is as follows: combustion occurs in chamber 26 near the top-dead-center position of piston 17, Le, when the piston 17 has moved to its leftmost operating position. Such combustion, together with any other energy in the engine 11 or the device 14 available to support the rightward movement of the power assembly 43, causes the piston 17 and the rest of power assembly 43 including the connecting part of the synchronizer-balancer assembly, rack member 46, to be moved to the right with respect to the engine housing, in a translational manner. Due to the rack and pinion arrangement 63, 64, 71, 72, 75 and 76, this translational movement to the right of the assembly 43, and thus the double-rack member 46, causes the counterbalancing movable weight portion of assembly 62, including the racks 75 and 76 and the movable wall members 73 and 74, to move to the left with respect to the housing 49, also in a translational manner.

As the power assembly 43 moves to the right, exhaust ports 42a will become uncovered, followed by intake ports 41a. Thus, the blow down of combustion gases in chamber 26, the proper scavenging of the chamber, and the introduction of a new charge ofair or fuel-air mixture will take place in known manner. During this same stroke to the right, the pressure in combustion chamber 31 increases due to the decreasing volume of combustion chamber 31. That is, air is compressed in combustion chamber 31 by the rightward movement of piston 17 until the air pressure and temperature in chamber 31 have been raised beyond the auto ignition point, at which time the fuel introduced into the chamber 31 by the fuel injector unit 32 will effectively burn in accordance with the principles of operation of conventional diesel engines. Of course, by using a conventional ignition system and a conventional carburetor or fuel injector system, the power sections can also be operated in accordance with the principles of conventional spark ignition or stratified charge engines.

Due to the increasing pressure of the gas within combustion chamber 31, and other energies available to support the leftward movement of power assembly 43, the rightward movement of power assembly 43 is stopped and it is caused to move to the left. During the leftward movement of piston 17 in cylinder 16, first the exhaust ports 42b are uncovered to allow the blow down" of the combustion gases within chamber 31, then the intake ports 41b are uncovered by the piston 17 so that the chamber 31 can be properly scavenged and a new charge of air or fuel-air mixture introduced into chamber 31.

Also during the leftward movement of piston 17, the ports 41:: within combustion chamber 26 are blocked by the piston 17. Thereafter, the ports 41b are blocked by the piston 17, and the air or fuel-air mixture in chamber 26 is compressed until combustion occurs in chamber 26, and the cycle of operation is repeated.

Thus, combustion chamber 26 and combustion chamber 31 are alternately acting in that gas within combustion chamber 26 is expanding and providing energy to the engine while gas within combustion chamber 31 is being compressed and accepting energy from the engine, and vice versa.

As noted above, during the rightward translational movement of the power assembly 43, with respect to the engine housing, the counterbalancing portion of assembly 62, including the racks 75, 76, and the movable wall members 73, 74 is translationally moved to the left with respect to housing 49. Conversely, when the power assembly 43 translationally moves to the left, the counterbalancing portion of assembly 62, including the racks 75, 76 and the movable wall members 73, 74, moves to the right. Moreover, as explained hereinabove, if the weights of the movable wall members 73, 74 are selected so that the product of the sum of the weights moving with the power assembly 43 times the length of the stroke of the assembly 43 is equal to the product of the sum of the weight of the counterbalancing portion of assembly 62, including the racks 75, 76 and the movable wall members 73, 74, plus the weight of the interconnected movable member of the energy absorbing device, times the distance through which the counterbalancing means of assembly 62 moves in the opposite direction of the piston 17, then dynamically balanced operation of the engine 1 1 can be achieved.

FIG. 4 Embodiment The engine 100, shown schematically in FIG. 4A, includes a double-acting power section 12 and a synchronizer-balancer section 13 which are substantially identical in structure and mode of operation to the power section 12 and the synchronizer-balancer section 13, respectively, of engine 11. Engine 100 is substantially identical to engine 11 of FIG. 1 except that the energy-absorbing device, represented diagrammatically in FIG. 1 by movable member 14, is specifically shown as a hydrostatic pump 104 driven by engine 100.

The pump 104 includes a pump housing 105 which may be integrally formed with the synchronizer housing 49, or may be separated from the engine as shown in FIG. 1. The housing 105 includes a pair of main bores 106 and 107 which are formed on opposite sides of the central longitudinal axis of the power assembly 43, and which have their central longitudinal axes aligned and disposed at an angle of substantially 90 with respect to the central longitudinal axis of the power assembly 43. The bore 106 is closed at its radially outer end, with respect to the central longitudinal axis of the power assembly 43, except for transverse inlet and outlet bores 108 and 109 which communicate with the bore 106 adjacent to its outer end. Similarly, bore 107 is closed at its radially outer end except for transverse inlet and outlet bores 111 and 112 which communicate with the bore 107 adjacent to its outer end. Conduits 113 and 114 connect the inlet bores 108 and 111, respectively, and thus the bores 106 and 107, respectively, with a source 115 of liquid to be pumped. Conventional check valves 116 and 117 are positioned in conduits 113 and 114 so as to permit flow of liquid only from the source 115 to the bores 106 and 107. Conduits 118 and 119 connect outlet bores 109 and 112, respectively, and thus the bores 106 and 107, respectively, with means 121 for utilizing or storing liquid under pressure. Conventional check valves 122 and 123 are positioned in conduits 118 and 119 so as to prevent liquid from returning to the bores 106 and 107 from means 121.

Plungers 124 and 125 are positioned for reciprocal transverse movement in the bores 106 and 107, respectively, and conventional seals, not shown, are used to prevent leakage between the plungers and the bores upon reciprocation of the plungers within the bores. Pumping chambers 126 and 127 are defined in the bores 106 and 107, respectively, between the radially outer ends of the bores and the radially outer ends of the plungers 124 and 125. As the plungers reciprocally move within their respective bores, liquid may be alternately sucked" into and expelled from the pumping chambers through their inlet and outlet bores, respectively, in a conventional manner.

Can followers 128 and 129 are mounted on the radially inner ends of plungers 124 and 125. A cam 131 is mounted within the housing for reciprocal movement therein in a direction substantially parallel to the central longitudinal axis of the power assembly 43. The cam 131 has a pair of cam surfaces 132 and 133 formed thereon and is designed so that the cam followers 128 and 129 remain in contact with the surfaces 132 and 133, respectively, at all times and so that the plungers 124 and always move in opposite or alternating effective pumping directions in their respective bores during the operation of the pump 104. This reduces the pressure waves in the discharge of the pump. Moreover, the cam surfaces 132 and 133 can be designed so that relatively uniform fluid velocities may be achieved in the discharge from the pump. Other pump designs or construction details may also be used.

The cam 131 is attached to move with the counterbalancing means of assembly 62 of engine 100. More specifically, as indicated in FIG. 4B, the shafts 93 and 94 connect with bosses 91 and 92 formed on movable wall members 73 and 74, respectively, of the synchronizer-balancer assembly 62 and also connect with the left end of the cam 131.

FIG. 5 Embodiment The engine 150, shown schematically in FIG. 5, includes a double-acting power section 12 and a synchronizer-balancer section 13 which are identical in structure and mode of operation to the power section 12 and synchronizer-balancer section 13, respectively, of engine 11 in FIG. 1. Engine is substantially identical to engine 11 except that the energy-absorbing device, represented diagrammatically by its movable member 14 in FIG. 1, is specifically shown in FIG. 5 as an electrical generator 151.

The generator 151 includes the generator housing 152 which, like pump housing 104, may be integral with the synchronizer housing 49. An annular stator arrangement 153, including a conventional core of magnetic material with windings of conductive material formed thereon, is positioned within the housing 152, and a conventional armature 154 is mounted for reciprocal movement within the stator arrangement 153 to magnetically coact with stator arrangement 153 in a conventional manner. Armature 154 is connected with the shafts 93 and 94 which move with movable wall members 73 and 74 in the identical fashion to that described with respect to FIG. 48.

Since the generator 151 may be of conventional design, further description thereof is not included herein. Again, however, one of the principal advantages of generator 151 as used with engines of the present invention is that the shape of the electrical wave or waves produced by the generator 151 during the leftward stroke of the armature 154, and thus the rightward stroke of the power assembly 43, is substantially identical to the shape of electrical wave or waves produced by the generator 151 during the rightward stroke of the armature 154. The electric generator, of course, may be of different design, e.g., member 154 may be a permanent magnet instead of an armature, and other variations may be used.

FIG. 6 Embodiment The engine 160, shown schematically in FIG. 6, includes a double-acting power section 12 and a synchronizer section 13 which are substantially identical in structure and mode of operation to power section 12 and synchronizer 13, respectively, of engine 11 in FIG. 1. The engine is substantially identical to engine 1 1 except that the energy absorbing device is specifically shown as a double-acting reciprocal compressor 161.

The compressor 161 includes a housing schematically shown at 162 with one end axially adjacent the synchronizer housing 49 and its end wall 51. Housing 162 also has a suitable end closure or wall member 163 at its other end. A compressor cylinder 164 is formed within housing 162 such that the central longitudinal axis of compressor cylinder 164 is coaxial with the central longitudinal axis of power cylinder 16 of power section 12, and thus of power assembly 43. A compressor piston 165 is positioned in the compressor cylinder 164 for translational reciprocating movement within the compressor cylinder 164 along said axis. A first compressor chamber 167 is formed between a right face 168 of compressor piston 165 and end wall 163. A second compressor chamber 169 is formed in the compressor cylinder 164 between a left face 171 of compressor piston 165 and end wall 51 of synchronizer section 13. A set of intake and discharge valves, two of which are shown at 172 and 173, respectively, are positioned in the housing 162 adjacent chamber 167 to permit the ingress of fluid to be compressed into chamber 167 and egress of compressed fluid from chamber 167. Similarly, a set of intake and discharge valves, two of which are shown at 174 and 175, respectively, are positioned in housing 162 adjacent chamber 169 to permit the ingress of fluid to be compressed into chamber 169 and the egress of compressed fluid from chamber 169.

Compressor piston 165 is connected with the shafts 93 and 94 which move with movable wall members 73 and 74 of the synchronizer-balancer assembly 62 in the identical fashion to that described with respect to FIG. 4B. Thus, during the leftward stroke of the counterbalancing part of assembly 62, gas or fluid within chamber 169 is compressed and discharged through valve 175 while, simultaneously, gas or fluid is being "sucked" into chamber 167 through intake valve 172. On the rightward stroke of the counterbalancing part of assembly 62, the gas or fluid in chamber 167 is compressed and discharged through discharge valve 173 while, simultaneously, gas or fluid is sucked into chamber 169 through intake valve 174, and the cycle is repeated.

These chambers may function independently or they may be connected in known manner to provide two alternating parallel first compressor stages or two successive series-connected first and second compressor stages. Special piston constructions, such as stepped pistons and cylinders (not shown), may be used for additional third or third and fourth stages, if desired.

As noted above, a major advantage of the engines according to the present invention is that they can provide twice the work output per cycle with the same capacity synchronizer and with substantially less than a factor of two increase in overall size and weight, as compared to prior engines needing a bouncer compressor as a primary source of return energy. This is illustrated by FIGS. 7 and 8. FIG. 7 shows pressurevolume curves for a prior engine having an output compressor and a bouncer compressor providing at least a substantial portion of the return energy necessary for sustained operation of the engine. FIG. 8 shows pressure-volume curves for the engines of the present invention. The notation ss represents the length of the swept stroke of the engine.

With respect to the output compressor curve of FIG. 7, at point 1 the compressor piston begins to compress fluid within the output compressor chamber, and the compressor piston continues to compress this fluid until point 2. At point 2, the output compressor discharge valves open and the continued movement of the compressor piston forces the compressed fluid from the output compressor at constant pressure. At point 3, the compressor piston is caused to reverse direction, and the output compressor discharge valves close. Between 3 and point 4 the pressure in the output compressor chamber rapidly drops as the volume increases behind the returning compressor piston. At point 4, the pressure within the output compressor chamber falls below atmospheric pressure, and the compressor inlet or suction valves open to admit the air which will be compressed and expelled during the next compressor stroke. As is well known in the art, the work done by the compressor piston is represented by the area under the curve 1, 2, 3. The work returned to the system by the compressor piston is represented by the area under the curve 3, 4, 1. Thus, the area enclosed by the curve 1, 2, 3, 4 is a measure of the output work done by the output compressor piston during a single cycle.

With reference to the bouncer compressor curve of FIG. 7,

by the bouncer compressor piston since the area beneath these curves is substantially equal under the assumed ideal conditions.

Thus, in FIG. 7, one side of a compressor piston acts as an output compressor piston and the other side acts as a bouncer piston, and the net work output per cycle is proportional to one times the area enclosed by the curve 1, 2, 3, 4. FIG. 8, by contrast, shows that if both sides of a compressor piston, such as sides 168 and 171 of piston 168, each act as output compressor pistons, as allowed by engines of the present invention, the net work output per cycle is proportional to two times the area enclosed by the curve 1, 2, 3, 4 which is twice the net work output as in the case represented by FIG. 7. Therefore, if other factors are equal, balanced, free piston engines according to the present invention provide twice the work output per cycle with substantially less than a factor of two increase in the overall size and weight, as compared to prior engines in which a bouncer-compressor is needed as a substantial source of return energy for a power piston, or for control purposes.

An additional advantage of the present invention, as described above, may now be graphically represented. FIG. 9 shows the velocity versus stroke relationship between the power assemblies of engines according to the present invention, in solid line 176, and prior engines, in dashed line 177, both with respect to the swept stroke ss of the engine. Both curves start at the origin, as it represents the left endpoint of the power assembly where the power assembly is at zero velocity. Both curves return to the axis at the right endpoint of their power assemblies where again the velocities are zero. As can be seen from a comparison of the two representations, the velocity upon the rightward stroke of engines according to the present invention, represented by the top half 178 of curve 176, is substantially identical to the velocity upon the leftward stroke, represented by the bottom half 179 of curve 176. As can also be seen, the velocity upon the leftward stroke of prior engines using bounce compressors, represented by the top half 183 of curve 177, is not equal to the velocity upon the leftward stroke, represented by the bottom half 185 of curve 177. Thus, engines according to the present invention have a naturally equal stroke-time function.

This naturally equal stroke-time function may be particularly important in association with certain energy-absorbing devices. For example, with respect to the energy-absorbing device in the form of the electrical generator 151 associated with engine 150, it was noted above that substantially identical wave forms were produced upon the rightward and the leftward stroke of the engine. As discussed, this is particularly important in alternating current wave generators, such as used with engine 150, to minimize the DC component of the generator output and in pumps, such as used with engine 100, to minimize the size of the dampers or accumulators used with the pump. Similarly, this naturally equal stroke-time function may be important for compressors such as used with engine 160.

FIGS. 10 and 11 Embodiments FIGS. 10 and 11 show two single-acting oppositely directed power sections which may be placed on opposite ends of an engine assembly according to the present invention to provide successive alternating power strokes to the engine in place of the one double-acting power section 12 shown connected to one end of synchronizer housing 49 in FIGS. 1, 4A, 5 and 6. For convenience, this embodiment has been shown as a specific modification of the engine and generator of FIG. 5. in order to position the single-acting power sections at the extreme ends of the engine combination, with both the synchronizer-balancer assembly and energy-absorbing device between them. In this construction, the connecting member 44 of the power assembly 43 need not penetrate through the cylinder head 24 of the right-hand or return power cylinder.

In FIG. 10, a single-acting power section is accordingly shown connected to the left end of housing 49 of the engine. Power section 180 is substantially identical in mode of operation to one-half of power section 12 of FIG. 1, and thus the operation of power section 180 will only briefly be discussed here. One difference between power section 180 and power section 12 is that a single-acting power piston 182 is positioned within power cylinder 16 of power section 180 instead of the double-acting power piston 17 positioned in power cylinder 16 of power section 12. Power piston 182 again has an outer face 18, and, in addition, power piston '182 has a recessed inner face 184 and a skirted sidewall 186. Another distinction between power section 12 and power section 180 is that power section 180 includes single-acting intake ports 41 and single-acting outlet ports 42 rather than the dual ports 41a, 41b and 42a, 42b of power section 12. Further, the power section 180 includes an integral, radially outwardly extending portion 187 which has a generally annular chamber 188 formed about the right end 189 of cylinder 16. The chamber 188 communicates with the end portion 191 of cylinder 16 to the right of the inner face 184 of the piston 182. The right end of housing portion 187, and thus the housing 15, are fastened to a wall 34 by a plurality of bolts, two of which are shown at 35, so the wall closes both the right end of chamber 188 and the lefl end of the synchronizer section 13.

Conventional one-way valves, one of which is shown schematically at 192, are positioned in the housing 15 and control the ingress of the air or fuel-air mixture into the chamber 188 of power section 180. Communication between the end portion 191 of the cylinder 16 and the chamber 188 permits the piston 182 to provide a scavenging pump action for the engine section 180. In other words, as the piston 182 moves to the left, from the position shown in FIG. 10, air or air-fuel mixture is drawn through the valve 192 into the chamber 188 and into the end. portion 191 of the cylinder 16. After combustion within chamber 26 drives or forces the piston 182 to move to the right, the piston compresses the air or mixture in the end portion 191 of the cylinder 16 and thus in the chamber 188 so that when the ports 41 and 42 are uncovered by the piston 182, the chamber 188 is a source of pressurized air or air-fuel mixture to scavenge the chamber 26.

A second oppositely directed single-acting power section is shown at 200 in FIG. 11. Power section 200 includes a singleacting power piston 202 which is arranged for translational reciprocating motion within cylinder 16, along the common central longitudinal axis of the engine. Power section 200 is substantially identical in construction and mode of operation to power section 180, except as noted herein and except that power section 200 is arranged to be alternately acting with power section 180. That is, power section 200 provides power to the engine on the power stroke of power piston 202 at the same time that power section 180 accepts power from the engine on the compression stroke of power piston 182, and vice versa.

Housing 187 of power section 200 is connected to the right end of housing 49. End wall 251 is shown as a separate piece rather than integrally formed with sidewalls 152 of housing 49 of synchronizer section 13. Instead, end wall 251 and the remainder of housing 187 of power section 200 are arranged to be attached to sidewalls 152 of housing 49 in the same fashion as housing 15 and wall 34 of power section 180 are attached to housing 49 in FIG. 10.

Power piston 202 is attached to move with double-rack member 46 by means of a shaft 48 and bolt 47. Shaft 48 is arranged in axial alignment with shaft 44 and therefore centrally penetrates wall 251. More particularly, wall 251 has a central aperture 58 formed therein which is in axial alignment with thecentral longitudinal axis of power section 200. Aperture 58 has conventional shaft seals 59 positioned therein to minimize the leakage of gas and lubricant between the shaft 48 and the aperture 58 upon reciprocation of the shaft 48.

Connection of the counterbalancing portion of the synchronizer-balancer assembly to the movable member of the energy-absorbing device may be made in a similar fashion to that previously discussed by extending shafts 93 and 94 outwardly around right-hand power section 200 through portions of wall 251, chamber 188 and housing wall 187 outside the combustion chamber in power cylinder housing 15. Alternately, a yoke may be attached to shafts 93 and 94 which yoke is then attached to the movable member of the energy-absorbing device. In FIGS. 10 and 11, however, the energy-absorbing device or generator 151 of FIG. 5 is specifically positioned between power sections and 200 such that the shaft 48 penetrates the movable member 154 of the energy-absorbing device at 220, while the shafts 93 and 94 attach to the movable member 154 of the energy-absorbing device just as in FIG. 5. (In FIG. 11, shaft 94 is not visible, because it is located directly behind shaft 48 in this view). In the light of the foregoing teachings, other energy-absorbing devices, in place of the electrical generator of FIG. 5, could also be located between the end power sections 180 and 200 of the embodiments of FIGS. 10 and 11. A particular advantage of the embodiments of FIGS. 10 and 11 is that identical power sections may be used to reduce the number of different parts which must be used to construct engines according to the present invention, and that no movable shaft need pass through head 24 of either of the power cylinders 16.

CONCLUSION From the foregoing, it is apparent .that a relatively lightweight, high-speed, balanced, free piston engine of simple design can be constructed utilizing the principles of this invention. As noted above, one of the important advantages of this invention is that such an engine, without the necessity of doubling the weight of its moving parts, provides rapid successive power strokes in both directions for high work output and a naturally equal stroke-time function on both strokes. Also, the same basic engine may perform as a power package to operate a variety of energy-absorbing devices.

Also, it should be noted that in addition to the alternately acting interconnected power piston members and the synchronizer-balancer assembly which constitute the main or principal operating members of the free piston engines of the present invention, the engine will also normally include other elements, some of which, such as oil pump pistons, water pump pistons, fuel pump pistons, scavenge pistons, and the like, may move either with or in the opposite direction to the power pistons during operation of the engines of the present invention. For example, an auxiliary oil pump piston could be attached to and moved with the walls 73, 74 of the synchronizer-balancer assembly 62, in the opposite direction to the power pistons, or the same oil pump piston could be attached to and moved with power assembly 43, in the same direction as the power pistons. Such auxiliary elements may also be driven by cams in directions other than along the axis of the translational movement of the power assembly and synchronizer-balancer assembly. Of course, the effective translational weight of any auxiliary piston or other movable member, i.e., that proportion of its weight which could be considered as having translational movement along said axis, must be included as a part of the weight of the counterbalancing portion of the synchronizer-balancer assembly or the power assembly, as the case may be, in order to balance the engine.

The terms reciprocating," reciprocal" or reciprocatory," as used herein in connection with a movable member of an energy-absorbing device, may include linear, swinging, rotary or other paths of movement which are not strictly or entirely along a straight line path parallel or corresponding to the longitudinal central axis of the engine cylinders. However, the weight to be attributed to such movable member in determining the total counterbalancing weight associated with the counterbalancing portion of the synchronizer-balancer assembly is only that proportional component of the total weight of the movable member which could be considered as having effective translational movement along such a straight line path.

It should also be obvious to those skilled in the art that the engines specifically described herein could be modified without affecting the principles of the present invention. For

example, other types of gears, linkages, or other mechanisms could be utilized in place of the preferred embodiment of the synchronizer-balancer assembly 62 shown. Other embodiments of the energy-absorbing devices shown herein may also be driven by such engines. Thus, I have described in the foregoing specification the background and nature of my invention and some of the ways in which the invention may be put into practice.

Now, therefore, I claim:

1. An unsymmetrical, synchronized, balanced, free piston engine arranged to drive a reciprocally movable member of an energy-absorbing device comprising, in combination: means for defining a first power cylinder, means for defining an oppositely directed second power cylinder, with the central longitudinal axis of the second power cylinder substantially coaxial to that of the first power cylinder; a first power piston mounted in the first power cylinder for translational reciprocating movement therein along said axis, the first power piston defining a first combustion chamber within the first power cylinder; a second power piston mounted in the second power cylinder for translational reciprocating movement therein along said axis, the second power piston defining a second combustion chamber within the second power cylinder, with the second combustion chamber arranged to be alternately acting with the first combustion chamber; the first power piston and the second power piston being interconnected for translational reciprocating movement together as a unit within the engine; a synchronizer-balancer assembly having a first movable portion mounted for translational reciprocating movement and connected to move together with the power pistons as a unit, and a second movable counterbalancing portion connected for synchronized translational reciprocating movement in a direction opposite to the direction of movement of the power pistons and first movable portion in response to movement of the first movable portion, the counterbalancing portion of the synchronizer-balancer assembly including means for driving connection to a movable member of an energy-absorbing device and having a preselected weight such that the absolute value of the product of the sum of the weight associated to move with the counterbalancing portion of the synchronizer-balancer assembly multiplied by the length of the stroke of the counterbalancing portion of the synchronizer-balancer assembly is substantially equal to the absolute value of the product of the sum of the weight associated to move with the power pistons multiplied by the length of the corresponding stroke of the power pistons.

2. The free piston engine of claim 1 having shaft means connecting the first movable portion of the synchronizer-balancer assembly to the power pistons, and wherein the central longitudinal axes of the shaft means, the first power cylinder, the second power cylinder, the first and second power pistons, the first movable portion and the counterbalancing portion of the synchronizer-balancer assembly are all coaxial.

3. The free piston engine of claim 1, wherein the movable counterbalancing portion of the synchronizer-balancer assembly comprises counter balancing movable weight means symmetrically distributed with respect to the common central longitudinal axis of relative translational movement of the power pistons.

4. The free piston engine of claim 1, wherein the energy-absorbing device is a pump.

5. The free piston engine of claim 4, wherein the pump includes at least one pumping chamber and at least one pumping plunger associated with the pumping chamber, and wherein the movable member of the energy-absorbing device includes a cam which causes the pumping plunger to move reciprocally within the pumping chamber in response to movement of the cam, said cam being connected for translational reciprocatory movement with the movable counterbalancing portion of the synchronizer-balancer assembly.

6. The free piston engine of claim 1, wherein the energy-absorbing device is an electrical generator.

7. The free piston engine of claim 6, wherein the movable member of the electrical generator is a reciprocating armature of the generator.

' 8. The free piston engine of claim 1, wherein the energy-absorbing device is a double-acting reciprocal compressor having a compressor housing with a compressor cylinder formed therein, and wherein the movable member is a compressor piston which is mounted in the compressor cylinder for translational reciprocating movement therein in a direction substantially parallel to'the longitudinal axis of the compressor cylinder, the compressor piston defining at least first and second compressor chambers within the compressor housing and the compressor cylinder.

9. The improved, free piston engine of claim 1, wherein the second power cylinder is adjacent to, coaxial with, and interconnected with the first power cylinder to form a double-acting power cylinder, wherein the first power piston and the second power piston are interconnected as parts of a single double-acting power piston member, and wherein the combination of the double-acting power piston and the doubleacting power cylinder form a double-acting power section.

10. improved free piston engine of claim I, wherein the first power piston and the first power cylinder comprise a first single-acting power section, wherein the first single-actin g power section is positioned adjacent an end of the engine, and wherein the second power piston and the second power cylinder comprise a second single-acting power section.

11. The improved free piston engine of claim 10, wherein the first combustion chamber is defined in the first power cylinder between the outer face of the first power piston and the closed outer end of the first power cylinder, and wherein the second combustion chamber is defined in the second power cylinder between the outer face of the second power piston and the closed outer end of the second power cylinder.

12. The improved free piston engine of claim 10, wherein the second single-acting power section is positioned on the extreme end of the engine opposite from the first single-acting power section.

13. The improved free piston engine of claim 1, wherein the first power cylinder and first power piston define the first combustion chamber at one end of the engine, the second power cylinder and second power piston define an oppositely acting second combustion chamber at the opposite end of the engine, and the synchronizer-balancer assembly is located between said combustion chambers.

14. The improved free piston engine of claim 13 having an energy absorbing device also located between said combustion chambers.

15. The improved free piston engine of claim 14 in which the energy-absorbing device and synchronizer-balancer assembly are located immediately adjacent each other between said combustion chambers.

16. The improved free piston engine of claim 3 having means for adjustment of the total weight of said counterbalancing movable weight means.

17. The improved free piston engine of claim 16 having means for removal of at least a portion of said counterbalancing movable weight means.

18. An unsymmetrical, synchronized, balanced, free piston engine arranged to drive a reciprocally movable member of an energy-absorbing device comprising, in combination: means for defining a first power cylinder section; means for defining an oppositely directed second power cylinder section with its central longitudinal axis substantially coaxial with the corresponding axis of the first power cylinder section; a first power piston reciprocable along said axis in the first power cylinder section, a second power piston reciprocable along said axis in the second power cylinder section; said first and second power pistons being rigidly interconnected for translational reciprocating movement back and forth as a unit along said axis; means for causing combustion alternately and successively in the respective power cylinder sections and thereby providing the reciprocating movement of said power pistons; a

synchronizer-balancer assembly having a first movable portion supported for translational reciprocating movement with said power pistons, a second movable counterbalancing portion, and means interconnecting said first and second movable portions for translational reciprocating movement of the second portion in a direction opposite to and coaxial with the direction of translational movement of the first movable portion and power pistons, said second portion of the synchronizer-balancer assembly having a weight greater than the weight required to counterbalance only the first portion of the synchronizer-balancer assembly, and said second portion also having means for driving connection of said second movable counterbalancing portion to a movable member of an energy-absorbing device.

19. An improved free piston engine according to claim 18, in which each of said portions has its mass symmetrically balanced with reference to their common central longitudinal axis of translational movement.

20. An asymmetrical, synchronized, balanced, free piston engine arranged to drive a reciprocally movable member of an energy-absorbing device comprising, in combination: first and second stationary power cylinder sections, first and second alternately acting power piston portions mounted for reciprocating movement in the respective first and second power cylinder sections, the first and second power pistons portions being interconnected for reciprocating movement together as parts of a power assembly in which all parts of the power assembly always move together as a unit; a synchronizer-balancer assembly having a first movable portion connected to move as a unit as part of the power assembly, and also having a counterbalancing second movable portion operatively connected to the first movable portion for reciprocating movement at all times in a direction opposite to the direction of movement of the first movable portion and in synchronism therewith; and a connection for connecting the reciprocally movable member of the energy-absorbing device to only the counterbalancing portion of the synchronizerbalancer assembly (as distinguished from the power assembly) such that the movable member of the energy-absorbing device moves as a unit with the counterbalancing portion of the synchronizer-balancer assembly and is driven by forces transmitted from the alternately acting power piston portions through the counterbalancing portion of the synchronizerbalancer assembly, the first and second portions of the synchronizer-balancer assembly having preselected relative weights such that the absolute value of the product of the sum of the weight associated to move with the counterbalancing portion of the synchronizer-balancer assembly multiplied by the length of its stroke is substantially equal to the absolute value of the product of the sum of the weight associated to move with the power assembly multiplied by the length of its corresponding opposite stroke.

21. A free piston engine according to claim 20 in which one of the movable portions of the synchronizer-balancer assembly has a weight greater than the weight required to counterbalance only the other movable portion of the synchronizer-balancer assembly. 

1. An unsymmetrical, synchronized, balanced, free piston engine arranged to drive a reciprocally movable member of an energyabsorbing device comprising, in combination: means for defining a first power cylinder, means for defining an oppositely directed second power cylinder, with the central longitudinal axis of the second power cylinder substantially coaxial to that of the first power cylinder; a first power piston mounted in the first power cylinder for translational reciprocating movement therein along said axis, the first power piston defining a first combustion chamber within the first power cylinder; a second power piston mounted in the second power cylinder for translational reciprocating movement therein along said axis, the second power piston defining a second combustion chamber within the second power cylinder, with the second combustion chamber arranged to be alternately acting with the first combustion chamber; the first power piston and the second power piston being interconnected for translational reciprocating movement together as a unit within the engine; a synchronizer-balancer assembly having a first movable portion mounted for translational reciprocating movement and connected to move together with the power pistons as a unit, and a second movable counterbalancing portion connected for synchronized translational reciprocating movement in a direction opposite to the direction of movement of the power pistons and first movable portion in response to movement of the first movable portion, the counterbalancing portion of the synchronizer-balancer assembly including means for driving connection to a movable member of an energy-absorbing device and having a preselected weight such that the absolute value of the product of the sum of the weight associated to move with the counterbalancing portion of the synchronizer-balancer assembly multiplied by the length of the stroke of the counterbalancing portion of the synchronizer-balancer assembly is substantially equal to the absolute value of the product of the sum of the weight associated to move with the power pistons multiplied by the length of the corresponding stroke of the power pistons.
 2. The free piston engine of claim 1 having shaft means connecting the first movable portion of the synchronizer-balancer assembly to the power pistons, and wherein the central longitudinal axes of the shaft means, the first power cylinder, the second power cylinder, the first and second power pistons, the first movable portion and the counterbalancing portion of the synchronizer-balancer assembly are all coaxial.
 3. The free piston engine of claim 1, wherein the movable counterbalancing portion of the synchronizer-balancer assembly comprises counter balancing movable weight means symmetricAlly distributed with respect to the common central longitudinal axis of relative translational movement of the power pistons.
 4. The free piston engine of claim 1, wherein the energy-absorbing device is a pump.
 5. The free piston engine of claim 4, wherein the pump includes at least one pumping chamber and at least one pumping plunger associated with the pumping chamber, and wherein the movable member of the energy-absorbing device includes a cam which causes the pumping plunger to move reciprocally within the pumping chamber in response to movement of the cam, said cam being connected for translational reciprocatory movement with the movable counterbalancing portion of the synchronizer-balancer assembly.
 6. The free piston engine of claim 1, wherein the energy-absorbing device is an electrical generator.
 7. The free piston engine of claim 6, wherein the movable member of the electrical generator is a reciprocating armature of the generator.
 8. The free piston engine of claim 1, wherein the energy-absorbing device is a double-acting reciprocal compressor having a compressor housing with a compressor cylinder formed therein, and wherein the movable member is a compressor piston which is mounted in the compressor cylinder for translational reciprocating movement therein in a direction substantially parallel to the longitudinal axis of the compressor cylinder, the compressor piston defining at least first and second compressor chambers within the compressor housing and the compressor cylinder.
 9. The improved, free piston engine of claim 1, wherein the second power cylinder is adjacent to, coaxial with, and interconnected with the first power cylinder to form a double-acting power cylinder, wherein the first power piston and the second power piston are interconnected as parts of a single double-acting power piston member, and wherein the combination of the double-acting power piston and the double-acting power cylinder form a double-acting power section.
 10. improved free piston engine of claim 1, wherein the first power piston and the first power cylinder comprise a first single-acting power section, wherein the first single-acting power section is positioned adjacent an end of the engine, and wherein the second power piston and the second power cylinder comprise a second single-acting power section.
 11. The improved free piston engine of claim 10, wherein the first combustion chamber is defined in the first power cylinder between the outer face of the first power piston and the closed outer end of the first power cylinder, and wherein the second combustion chamber is defined in the second power cylinder between the outer face of the second power piston and the closed outer end of the second power cylinder.
 12. The improved free piston engine of claim 10, wherein the second single-acting power section is positioned on the extreme end of the engine opposite from the first single-acting power section.
 13. The improved free piston engine of claim 1, wherein the first power cylinder and first power piston define the first combustion chamber at one end of the engine, the second power cylinder and second power piston define an oppositely acting second combustion chamber at the opposite end of the engine, and the synchronizer-balancer assembly is located between said combustion chambers.
 14. The improved free piston engine of claim 13 having an energy absorbing device also located between said combustion chambers.
 15. The improved free piston engine of claim 14 in which the energy-absorbing device and synchronizer-balancer assembly are located immediately adjacent each other between said combustion chambers.
 16. The improved free piston engine of claim 3 having means for adjustment of the total weight of said counterbalancing movable weight means.
 17. The improved free piston engine of claim 16 having means for removal of at least a portion of said counterbalancing movable weight means.
 18. An unsymmetrical, synchronized, balanced, free pisTon engine arranged to drive a reciprocally movable member of an energy-absorbing device comprising, in combination: means for defining a first power cylinder section; means for defining an oppositely directed second power cylinder section with its central longitudinal axis substantially coaxial with the corresponding axis of the first power cylinder section; a first power piston reciprocable along said axis in the first power cylinder section, a second power piston reciprocable along said axis in the second power cylinder section; said first and second power pistons being rigidly interconnected for translational reciprocating movement back and forth as a unit along said axis; means for causing combustion alternately and successively in the respective power cylinder sections and thereby providing the reciprocating movement of said power pistons; a synchronizer-balancer assembly having a first movable portion supported for translational reciprocating movement with said power pistons, a second movable counterbalancing portion, and means interconnecting said first and second movable portions for translational reciprocating movement of the second portion in a direction opposite to and coaxial with the direction of translational movement of the first movable portion and power pistons, said second portion of the synchronizer-balancer assembly having a weight greater than the weight required to counterbalance only the first portion of the synchronizer-balancer assembly, and said second portion also having means for driving connection of said second movable counterbalancing portion to a movable member of an energy-absorbing device.
 19. An improved free piston engine according to claim 18, in which each of said portions has its mass symmetrically balanced with reference to their common central longitudinal axis of translational movement.
 20. An asymmetrical, synchronized, balanced, free piston engine arranged to drive a reciprocally movable member of an energy-absorbing device comprising, in combination: first and second stationary power cylinder sections, first and second alternately acting power piston portions mounted for reciprocating movement in the respective first and second power cylinder sections, the first and second power pistons portions being interconnected for reciprocating movement together as parts of a power assembly in which all parts of the power assembly always move together as a unit; a synchronizer-balancer assembly having a first movable portion connected to move as a unit as part of the power assembly, and also having a counterbalancing second movable portion operatively connected to the first movable portion for reciprocating movement at all times in a direction opposite to the direction of movement of the first movable portion and in synchronism therewith; and a connection for connecting the reciprocally movable member of the energy-absorbing device to only the counterbalancing portion of the synchronizer-balancer assembly (as distinguished from the power assembly) such that the movable member of the energy-absorbing device moves as a unit with the counterbalancing portion of the synchronizer-balancer assembly and is driven by forces transmitted from the alternately acting power piston portions through the counterbalancing portion of the synchronizer-balancer assembly, the first and second portions of the synchronizer-balancer assembly having preselected relative weights such that the absolute value of the product of the sum of the weight associated to move with the counterbalancing portion of the synchronizer-balancer assembly multiplied by the length of its stroke is substantially equal to the absolute value of the product of the sum of the weight associated to move with the power assembly multiplied by the length of its corresponding opposite stroke.
 21. A free piston engine according to claim 20 in which one of the movable portions of the synchronizer-balancer assembly has a weight greater than the weight required to counterbalance only the otheR movable portion of the synchronizer-balancer assembly. 